Piston ring forming apparatus



E. R. WEEK, JR

PISTON RING FORMING APPARATUS May 14, 1940.

Filed March 12, 1937 Patented May 14, 1940 UNHTED STATES PATENT OFFICEEdmund R. Week,

In, Oakland, Calif.

Application March 12, 1937, Serial No. 130,545

5 Claims.

I The invention relates to apparatus for formmg and manufacturing pistonrings. This applicationis a continuation-in-part of my co-penda. ingapplications, Serial Numbers 742,033 and 742,220, filed August 30, 1934,and August 31, 1934, respectively.

Piston rings of internal combustion engines may be divided roughly intotwo classes, the single one piece type and the multiple piece type.

The former belongs to a class comprising a single annular ring, as ofcast iron or the like, which is mounted in a ring groove in the pistonand serves by its own resilience to expand outwardly from the ringgroove into sealing engagement with the cylinder wall. This type of ringby reason of its simplicity and relative cheapness has found a very wideusage in internal combustion engines. However, as may be understood, asingle piece ring must have the dual qualities of resilience so as tofirmly urge the ring against the cylinder wall and in addition have aproper bearing surface against the cylinder walls for procuring a smoothand uninterrupted seal. As

, may be also understood, these qualities of resilionce and bearingsurface are not necessarily or normally found together in a single metaland accordingly a plurality of members having specially selected metalsto accomplish separately I the functions of resilience and cylinderengagerings have been found to function remarkably well and at aconsiderably higher efficiency than the first mentioned type. Especiallyis this true at higher engine speeds where the relatively poorresilience of the one piece ring is incapable of preventing anexcessively high blow-by of products from the combustion chamber of thecylinder into the crank case.

While the multiple piece, spring type of ring is capable of affordingthese and many other important advantages over the simple one piece ringfirst mentioned, the multiple piece ring ordinarily involves in itsconstruction the use of relatively small cylinder engaging rings and theconstruction of these small rings to withstand the high pressures andtemperatures obtaining in This type of ring makes the cylinder has beena source of weakness in these rings. At first attempts were made to castor machine these relatively small rings from cast iron, but they werefound much too brittle to give lasting service and would, after arelatively short period of use, be broken. Attempts followed the use ofcast iron in the field of bronze but it was found that when thissubstance was cast the same was substantially as brittle as: the castiron and relatively unusable. Also, when the bronze rings were drawn rextruded they were much too soft, were quickly mutilated, and consumedby oxidation and disintegration.

Applicant has found through exhaustive tests extending over a protractedperiod of experimentation that these small cylinder engaging rings ofthe multiple piece type should be as substantially as hard as thecylinder wall that they engage, or if there is any difference inhardness that it should be on the softer side, preferably not exceedingfrom to points on the Rockwell B scale. It has been demonstrated that ifthese small rings are materially harder than the cylinder side walls,they will have an abrasive action thereon tending to scratch and deformthe cylinder. On the other hand, if such rings are materially softerthan the cylinder wall, they permit the embedding and seating ofparticles of dust and other foreign substances which in turn have anabrasive action on the cylinder side wall. Furthermore, it has beenfound that coordinated with the aforesaid hardness: the rings must be ofmaximum toughness so as to resist wear and deformation. Also, thesesmall rings should be of low resilience and relatively flexible so thatsubstantially the total resilience of the ring will reside in the bodyring and the smaller rings will be uniformly pressed outwardly by thebody ring into close conformity with the cylinder walls. In addition,the rings should have a substantially different fineness of surfacegrain structure and texture than the cylinder walls so as to aiford alow coefficient of friction therebetween.

In satisfying the above conditions, attempts have been made to usematerials such as steel in one form or another, but while the hardnessof the ring was thus obtained, the other desired characteristics did notfollow. Tempered high carbon steels in most instances were too hard, tooabrasive and much too stifi and resilient. Annealed steels proved toosoft, became mutilated and of little use. In accordance with myinvention, however, and as a principal object thereof, I have providedfor the use of materials such as steel in the construction of thesesmall rings by initially selecting a certain hardness and carbon orother alloy content and then processing and working the metal in a wayas to retain and increase its hardness to approximately that of thecylinder side wall with which it is used, to greatly increase itstoughness, to introduce a necessary degree of pliancy and to maintainits resilience low.

Another object of the invention is to provide an apparatus for causingthe desired fabrication of the metal as aforesaid simultaneously withand by the same operations involved in fabricating the ring structureand thereby not only to greatly simplify the manufacture of the ring butalso utilize the changing molecular arrangement involved in thefabrication of the steel to effect a greatly improved construction inthe cylinder engaging edge and the free ends of the ring.

A further object of the invention is to provide an apparatus for formingon rings of the character described minute annular beads extendingaround the cylinder engaging wall and which serve to provide almost fromthe very outset a proper seating of the ring against the cylinder wall.

Still another object of the invention is to provide an apparatus of thecharacter described which will in a single advance movement of a diecompletely form a ring of the character above set forth.

The invention possesses other objects and features of advantage, some ofwhich, with the foregoing, will be set forth in the followingdescription of the preferred form of the invention which is illustratedin the drawing accompanying and forming part of the specification. It isto be understood, however, that variations in the showing made by thesaid drawing and description may be adopted within the scope of theinvention as set forth in the claims.

Referring to said drawing:

Figure 1 is a cross sectional view of a multiple piece type ring in theforming of which the apparatus of the present invention is particularlyused. the ring being here shown operatively positioned in the ring andcylinder.

Figure 2 is a side view of the bending and rolling device used inconnection with the present invention.

Figure 3 is a plan view of a ring loop as placed in the die for formingby the die.

Figure 4 is a side elevation of one part of a die constructed inaccordance with the present invention.

Figure 5 is a sectional elevation view of a cooperating part of the die.

Figure 6 is a transverse sectional view of a part of the die memberillustrated in Figure 4 and is taken substantially on the plane of line66 of Figure 4.

Figure '7 is an enlarged fragmentary sectional view of opposed ringconnecting surfaces of the die.

Figure 8 is a fragmentary plan view of a part of the ring formed by thedie.

Figure 9 is a transverse sectional view of the ring illustrated inFigure 8 and is taken substantially on the plane of line 99 of Figure 8.

The piston ring shown in Figure l of the drawing is illustrative of amultiple piece type ring referred to in the foregoing. The ring hereshown is of an improved form which has been more fully described andclaimed in my co-pending applications aforesaid and includes a resilientbody or main ring II which carries one or more side cylinder engagingrings l2. The body ring by reason of its appreciable size and inclusionof resilience is not of critical construction from a strength andwearing standpoint as are the smaller side rings l2. It is with theseside rings that the present invention is primarily concerned and in themaking of these small rings strong, durable, and possessive of otherdesirable characteristics hereinbefore mentioned. However, as will beunderstood, the apparatus of the present invention may be used for makinother piston rings of a different character.

As here shown, the side cylinder engaging rings are of substantiallysquare or rectangular cross section and for simplicity in theconstruction of these rings. I prefer to use a steel wire l3 which iscommercially square and of cross sectional dimensions somewhat largerthan the finished dimensions of the ring. In accordance with the presentinvention, I select a drawn annealed steel wire of 50 to 65 pointhardness of the Rockwell B scale and which has about 1 per cent carboncontent. This wire at the outset is too soft for immediate use as apiston ring but when treated and formed by the apparatus of the presentinvention the metal is hardened to approximately the hardness of thecylinder wall and is worked to increase its toughness.

The wire is first fed into a bending and rolling machine M which is ofconventional design including an enlarged and grooved roller it whichcooperates at its circumference with smaller wire confining and bendingrollers 21. The wire is delivered from the rollers in a helicalformation and is cut into single unit coils l8. Preferably in cuttingthe coils, the free ends 29 thereof are arranged, with the radiallyouter edges 2| thereof cut diagonally ahead of the inner edges 22. Also,will be understood the bending of the normally straight wire into acircular formation will cause by relative crowding and expansion of thematerial respectively at the inner and outer circumferential, axiallyextending, sides with a corresponding increase and decrease of theaxially extending dimensions of such sides. This has the effect ofdistorting the cross-sectional shape of the ring as indicated roughly indotted lines in Figure 9 from which shape the ring is cut and pressedinto a sharply defined square by means of the die and as shown in fulllines of Figure 9.

The loops !8 when cut as above, are ready for working and forming intothe final product. Such operations are arranged, in accordance with myinvention to be effected by a single die 23 and by a single advancemovement of the die. The latter, as here shown, consists of male andfemale sections 24 and 26 which are arranged for interengagedpositioning for forming and working the ring therebetween. The femalemember is of stationary construction and includes a base support 21having a recess 28 for the receipt of a removable annular die block 29and is formed centrally therethrough with a guide bore 3!. Formed in theblock and opening jointly to the top and inner surface thereof is anannular ring seat 32 for receipt of the loop l8 and is arranged tocooperate with the male section to compress and form the ringtherebetween.

The male section of the die is arranged for mounting in a press andcomprises a guide portion 33, a skirt 34 surrounding and longitudinallyspaced from the portion 33 and an annular shoulder abutment 36surrounding an end of the skirt, the portion 33. skirt and abutmentbeing substantially concentrically arranged and adapted for movementinto the guide bore 3|, the recess 28, and the seat 32 respectively ofthe female die section. In accordance with the present arrangement thestock from which the ring is made somewhat wider in radial thicknessthan the finished ring, as indicated by the dotted lines in Figures 3and 9. On the other hand, the base or end Wall 39 of the seat 32 is of awidth corresponding to the finished radial thickness of the ring withthe result that when the loop I8 is first placed in the seat 32 an innerportion 20 of the loop will overlie the inner circumferential surfacesof the die block 29 and overhang the wall 30 ofthe seat. Thus, onlowering of the die section 26 the end wall of the skirt 34 is broughtinto engagement with the inner portion 20 of the ring loop and shearsthis portion from the remainder of the ring. The skirt 34 is providedwith a longitudinal peripheral recess which extends from the end 35 tothe shoulder 36 and leaves at the portion 2!] of the loop an in- Wardlyprojecting lug which is arranged to engage in a suitable opening (notshown) in the body ring I l for preventing relative rotation between thebody and side rings.

The skirt 34 is formed with a small downwardly convergent taper (in thepresent case about 4 v degrees) which is effective to engage the innerperiphery of the loop and expand the same against the outer peripheralwall 31 of the ring seat 32. Preferably the taper is confined to thelower portion 34 of the skirt, whereas the portion 34 of the skirtadjacent the shoulder 36 and opposite the side wall 31 in the finalposition of the die is formed parallel to the surface 31 and at rightangles to the shoulder 36 so that the final form of the ring will beperfectly square and prior to the final forming of the ring the same issub jected to a considerable radial compression or swedging between thetapered side 34' and the seat side 31. However, in certain types ofrings it is desirable to form the inner and outer peripheral surfacesthereof in an inclined relation so as to produce a turning out of thering against the cylinder Wall and in the formation of such rings it maybe desirable to extend the taper of the skirt substantially completelyto the shoulder I 36 so as to affect the final shape of the ring.

During this radial compression or swedging of the ring the same is freeto expand circumferentially and also to expand axially between the diesurface 30 and 36 which, during the swedging operation are spaced by aconsiderable distance. At the end of the swedging operation, that is,after the tapered portion34' has passed the seat side 30, the shoulder36 is brought sharply against the top surface of the ring and the ringis compressed by the opposed surfaces 30 and 36 of the ring enclosureunder a tremendous axial pressure corresponding to an axial force ofapproximately 40 to 60 tons for the average size automotive ring. Duringthis compression the ring is held against radial expansion by theopposed sides 34" and 37 of the ring enclosure and, as the result thematerial of the ring is forced to fiow in a circumferential directiontowards the free ends of the ring. Preferably, in order that the outercylinder engaging side 39 of the ring may have the top edge thereofsharply defined, the base or end wall 30 of the ring seat is formed witha rise or upstanding annular shoulder 4! adjacent the wall 31 fordepressing and sharply defining the outer edge of the ring top surface42. This extra depression of the outer portion of the ring has furtherand very important ad-, vantages in the forming of the ring, in that theextra circumferential flow of material caused by this depressionproduces a greater proportionate fiow of material at the outer surfaceof the ring than at the inner surface thereof, and thereby causes agreater circumferential advancement of the outer edges 2! of the freeends of the ring than of the inner edges 22 with the result that thering will be progressively curved inwardly from the normal circumferencethereof towards the free ends of the ring and the latter will be drawnwell within the circumference of the ring. This feature is of particularadvantage since these outer edges are sharply defined and have been asource of nuisance in the past in that they required either filing downor rounding on to prevent their digging into and scratching the cylinderwall. In accordance with the present invention, however, and as aboveexplained, these ends are automatically withdrawn from the circumferenceof the ring as indicated in Figure 7 and are thus removed from immediatecontact with the cylinder wall,

The flow of material circumferentially has an additional effect on thering in that it changes the texture of the outer cylinder engagingsurface thereof. Since there is a relative shearing of material causedby the different degrees of material flow aforesaid, it Will beunderstood that the tendency of such flow is to elongate the metalfibers in the direction of shear. This has the eifect of changing therather granular structure of the original steel wire into a vastlytougher, denser and fibrous or grain structure which in addition, sinceit contrasts with the surface texture of the cast cylinder wall, affordsa low coefiicient of friction between the cylinder wall and the pistonring.

As an important feature of my invention, the ring is set, during thecompressions aforesaid, to a diameter closely corresponding to that ofthe cylinder with which the ring is to be used. In this manner anyrequired expansion or contraction of the ring to constantly engage thecylinder wall will be but slight from its set diameter and will not bematerially resisted by the ring. Thus as will be clear, the ring will befree for expansion against the cylinder wall by the body ring and willas readily be retractable to conform to minor variations in cylinderbore diameter. This setting is effected by raising the stress on thering to a point above its elastic limit, so that the same will retainthe shape imparted to it by the die. of the ring fibers is productive ofa certain degree of flexibility which permits the latter to more closelyfollow any variations in the cylinder.

A further and most important feature of the compression aforesaid liesin the raising of the hardness of the ring metal. As hereinbeforepointed out, it is highly desirable that the hardness of the ringclosely approach that of the cylinder side walls. I have found that theaverage hardness of such side walls is about from to points on theRockwell B scale. While the original wire had a hardness of but 50 to 65points, the same is hardened by the compressions aforesaid toapproximately 95 points, this being preferable to maintain the ringslightly on the soft side on a balance hardness with the cylinder wall.Preferably a pair of greater surfaces 48 and 45 of the die sections areengaged at the end of movement to limit the size of the annular ringenclosure and to cause a positive and accu- Also this straining jacentthe depression 32.

rate end position of male section and relieve the engaged portion of thering enclosure and to render the rings formed substantially identicalwithin approximately .0025 or less in mass pro duction.

a further important feature of the present apparatus, the same isarranged to form around the circumferential outer side 39 of the ring aplurality of minute annular beads 43 which initially engage the cylinderwall and provide a perfect quick seating of the ring thereagainst andare thereafter quickly worn away to provide a permanent sealedengagement of the ring against the cylinder wall. As here shown, thesebeads are formed by the provision of a plurality of minute annularrecesses M in the side wall 37 of the ring seat so as to allow the flowof material into such recesses during compression of the ring and theformation of the aforesaid beads. The size of both the beads and therecesses has been enlarged in the accompanying drawing and even in theenlarged illustration of the Figure 7, in view of clarity. However, aswill be understood, these beads and recesses are 4 extremely small andare scarcely detectible except upon close inspection of the ring.Preferably one of the recesses id is provided directly at theintersection of the wall 3? and the shoulder 4! so as to form acorresponding head on the ring at the upper outer corner immediately ad-In this position the head has an additional action which is ofconsiderable value.

I claim:

1. A member provided with a cylindrical bore and an enlarged seatadjacent an end of the bore for receipt of a generally round unfinishedpiston ring having a radial ring thickness greater than said seat so asto overlie said bore, a second member having a generally cylindricalportion extendable into said bore and adapted to engage said ring andshear therefrom a portion of said ring overlying said bore, said secondmember having a longitudinal recess at the periphery thereof to leave aninwardly extending lug on said ring.

2. A member provided with a cylindrical bore and an enlarged seatadjacent an end of the bore for receipt of generally round unfinishedpiston ring having a radial ring thickness greater than said seat so asto overlie said bore, a second meming a longitudinal recess at theperiphery thereof to leave an inwardly extending lug on said ring, theperiphery of said second member being provided with a longitudinal taperso as to cause a radial swedging of the ring against the side of saidseat.

3. A die for forming a piston ring comprising, a member having a boreand formed with an enlargement at an end thereof defining an annularseat for an unfinished ring, said seat having a transverse end wall anda peripheral side wall for supporting said ring, a second member havinga portion movable into said bore in opposed relation to said seat sidewall and engageable with the inner side of said ring to confine the sameagainst said seat side wall, and means extending transversely from saidportion and movable in the direction of said seat end wall to compresssaid ring thercagainst, said seat side wall being provided with a smallannular recess to form an annular head on the outer side of said ring.

4. A die for forming a piston ring comprising, a member having a boreand formed with an enlargement at an end thereof defining an annularseat for an unfinished ring, said seat having a transverse end wall anda peripheral side wall for supporting said ring, a second member havinga portion movable into said bore in opposed relation to said seat sidewall and engageable with the inner side of said ring to confine the sameagainst said seat side wall, and means extending transversely from saidportion and movable in the direction of said seat end wall to compresssaid ring ther against, said seat side wall being provided with aplurality of annular recesses to form beads on the outer side of saidring.

5. A die for forming a piston ring comprising, a member having a boreand formed with an enlargement at an end thereof defining an annularseat for an unfinished ring, said seat having a transverse end wall anda peripheral side wall for supporting said ring, a second member havinga portion movable into said bore in opposed relation to said seat sideWall and engageable with the inner side of said ring to confine the sameagainst said seat side wall, and means extending transversely from saidportion and movable in the direction of said seat end wall to compresssaid ring thereagainst, said end wall being provided with an upstandingannular shoulder adjacent the outer edge thereof, said seat side wallbeing provided with an annular recess at the outer edge of saidshoulder.

EDMUND R. WEEK, JR.

